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Title: Constraints of no-till dryland agroecosystems as bioenergy production systems

Author
item MINER, GRACE - Colorad0 State University
item HANSEN, NEIL - Colorad0 State University
item INMAN, DANIEL - National Renewable Energy Laboatory
item Sherrod, Lucretia
item PETERSON, GARY - Colorad0 State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2012
Publication Date: 1/29/2012
Citation: Miner, G.L., Hansen, N.C., Inman, D., Sherrod, L.A., Peterson, G.A. 2012. Constraints of no-till dryland agroecosystems as bioenergy production systems. Agronomy Journal. 105:364-376.

Interpretive Summary: The objective of this study was to evaluate the capabilities and constraints of harvesting residues from dryland systems. The study used observations from a long-term experiment in Colorado to examine biomass production from wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum [Sorghum bicolor (L.) Moench] at three no-till sites in a winter wheat–corn–fallow (WCF) or winter wheat–sorghum–fallow cropping system. For dryland cropping systems in the semiarid Great Plains, wind erosion and maintenance of soil organic C are major constraints to harvesting stover as a biomass feedstock. The removal of corn stover in a WCF rotation created a much greater wind erosion risk than the removal of wheat straw based on a simulation modeling exercise. Biomass harvest of residues from dryland grain crops was not identified as a sustainable practice from the perspective of soil C, even without consideration of other factors such as net energy budgets.

Technical Abstract: Soil erosion and loss of soil organic C (SOC) may limit the sustainable harvest of crop residues for biofuels from dryland systems in the semiarid Great Plains. The objective of this study was to evaluate the capabilities and constraints of harvesting residues from dryland systems. The study used observations from a long-term experiment in Colorado to examine biomass production from wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum [Sorghum bicolor (L.) Moench] at three no-till sites in a winter wheat–corn–fallow (WCF) or winter wheat–sorghum–fallow cropping system. Modeling evaluated the impact of residue removal on erosion rates and SOC dynamics. The Revised Universal Soil Loss Equation and the Wind Erosion Equation were used to simulate erosion, and the DAYCENT model was used to estimate changes in SOC with residue removal. Biomass yield for WCF averaged 3.8 Mg ha–1, divided into stover and grain yields of 2.2 and 1.6 Mg ha–1. Water erosion was not shown to constrain residue harvest, but modeling indicated unsustainable wind erosion rates after removing 10 to 30% of corn residue. Simulations showed that up to 80% of wheat straw could be harvested without exceeding sustainable wind erosion rates. The major constraint to sustainable residue harvest is a residue return rate of 2.4 Mg ha–1 yr–1 of biomass to maintain SOC.